Method of manufacturing colored oriented articles from acrylonitrile polymers and copolymers



United States Patent METHGD 0F MANUFACTURING COLGRED ORI- ENTET) ARTELES F R 0 M ACRYLONITRILE PQLYMERS AND C UPOLYMERS Artur Stoy, 7 l ar-iii, Prague 6, Czechoslovakia, and Marta Sivolrovzi, 134d Sezemicka, Pardubice, Czechoslovakia No Drawing. Filed Apr. 21, 1961, Ser. No. 104,509

Claims priority, application tlzechoslovainia Apr. 25, 1960 11 Claims. (Cl. 8-55) Oriented articles such as fibres or filaments from acrylonitrile polymers and copolymers containing at least 80 percent of acrylonitrile component, generally known as acrylic fibres, may be dyed only with some difficulties. The fibres are crystalline and hydrophobic, and if they possess no basic groups, they are incapable of binding acid wool dyestuffs. Thus they may be dyed only by means of cuprous ions forming a complex bond between the nitrile group -CN and the sulfonic group of the dyestuli. Basic and direct dyestuffs may be used, but in boiling aqueous coloring baths the obtained hues are rather light. For deep colors the dyeing is to be carried out in an autoclave at temperatures above 100 C. The assortment of suitable dyestuffs is rather narrow and the above mentioned methods are less convenient and more expen sive than usual methods of dyeing e.g. cotton or rayon.

It is known that an unoriented or poorly oriented acrylic fibre may be dyed rather easily, if the coloring bath is applied during the spinning process or immediately after spinning, when the fibre is still swollen with remaining solvent or with the coagulating bath respectively. Such possibility of dyeing is mentioned e.g. in the US. patent specification No. 2,558,735. Spinning polyacrylonitrile solutions in dimethyl formamide directly into an aqueous dyeing and coagulating bath Was also described. The first mentioned method has the disadvantage that the swollen non-oriented acrylic fibre has a very low tenacity, so that the dyeing in a separate bath placed between the coagulating bath and a hot aqueous bath, in which the fibre is then stretched, is rather dificult. Admixture of dyestuffs directly into the first coagulating bath has the disadvantage that the recuperation of the solvent is more complicated and the consumption of dyestuffs is increased. Easily soluble acid dyestufis are not suitable for this meth od since they are not bound firmly in the fibre, which is unoriented, amorphous and rather porous. The dyestuifs are thus rather easily liberated in any subsequent aqueous bath and also during the drying process. Particularly the hot stretching bath dissolves the most part of the nonfixed acid dyestufi. It is thus very difficult to obtain level deep colors.

Now it has been found that practically all known dyestuffs may be used for dyeing acrylic fibres and other oriented articles such as bands, strips, strings and similar to obtain all hues, light and deep, at temperatures under 100 C., if rubbery acrylonitrile polymers or copolymers, plastified with from 65 to 85 percent of aqueous highly concentrated inorganic salt solutions, are extended to about from 200 to 900 percent of their original length and washed in extended condition in order to remove at least a substantial part of the salts therefrom and dyed simultaneously or subsequently before the fibre structure is set.

Suitable inorganic salts are zinc chloride, sodium or potassium rhodanide, lithium bromide and similar salts, either alone or mixed with other salts such as calcium chloride, magnesium chloride, aluminum nitrate and the like. Said salts are dissolved eg in water which may be partially or fully replaced by organic liquids capable of dissolving the salts, e.g. by methanol or ethanol.

The setting or stabilization mentioned above is meant to indicate the reaching of a staple state in which super- "ice fluous water and other non-dissolving liquids are mostly removed, intermolecular cohesion bindings established and some crystallinity developed. The reaching of such stable state can be noticed most easily by that the oriented article is no more stained by acid dyestuffs in aqueous solution at room temperature. The transition from an unstable to the stable state is rather sharp and the interval, during which the article, such as fibre may be dyed, depends on the extension percentage, i.e. on the degree of orientation. So e.g. if a thick rubbery monofilament made from pure polyacrylonitrile is extended to 700 percent of its original length, washed for 15 minutes in distilled water at 22 C. and then dyed, the interval between the washing and dyeing must not exceed 3 minutes. During these 3 minutes the fibre is colored almost immediately and in full extent as if it has been washed directly in a dyeing bath of the same concentration of the same acid dyestutf. Thereafter, in a rather short interval of several minutes, the fibre is colored unevenly and insufficientiy. Later on, after about 6 minutes from the beginning, the fibre is not more colored at all. If, however, the same filament has been extended to 400 percent only, the interval after the washing, during which it can be easily dyed, lasts about 4 min utes. At an extension to 200 percent only said interval lasts about 22 minutes. Thus it is evident that the setting of an oriented fibre formed by the above described method lasts at least several minutes in dependence on the degree of orientation (i.e. on the stretching of the rubbery article before washing) and that the polyacrylonitrile fibre or filament can be easily dyed during this interval.

Although it is possible to dissolve dyestuffs d rectly in the bath with which the elastomeric extended filament or similar is firstly contacted, it is more convenient to use a separate dyeing bath. So e.g. a bundle of elastomerie filaments is stretched to a desired degree, led continuously through a washing liquid such as distilled water, diluted aqueous solution of the same salts which are contained in the filament, methanol or the like, and then through a dyeing bath. The use of a separate dyeing bath makes the recuperation of waste salts more economical.

The temperature of the bath is not critical; the dyeing can be performed during several seconds till to several minutes at room temperature, according to the desired coloration depth. More elevated temperature may somewhat increase the rate of dyeing, but the total amount of the dyestutl taken from the bath is then decreased. The unusual rapidity of dyeing can be explained only by the transitory open structure of the fibre prior reaching a stable crystalline state. This phenomenon of the transitory state before setting was not known before and could be scarcely detected by another method than by dyestuii or iodine sorption. The X-ray method is here useless since the exposure times are much longer than the duration of said phenomenon.

The separate dyeing after washing out the salts is advantageous also because even such acid dyestuffs can be used which form usually precipitates with inorganic acids or with metal ions, particularly with zinc or calcium ions.

Elastomeric plastified acrylic fibres or other oriented articles containing about 15 to 35 percent polymeric substance and from about 65 to percent: of highly con centrated inorganic salt solutions may be prepared in diiierent ways. It is possible, for instance, to spin a solution of acrylonitrile polymers or coplymers in saturated zinc and calcium chloride solution (1:1 till to 3:1 in volume) into a diluted aqueous or methanolic solution of the same salts, acidified with a small amount of hydrochloric acid in order to avoid zinc chloride to be hydrolyzed. The path of the filament in the coagulating bath is to be chosen such that the filament is only coagulated, whereat it still contains from fibOUll 65 to 85 stirring vigorously.

percent of the brine. The filament is then kept dry for some time until it becomes elastorneric.

Another method of manufacturing rubbery filaments or similar articles such as bands or strips, capable of being oriented and dyed in the manner disclosed above consists in polymerizing or copolymerizing acrylonitrile directly in a brine capable of dissolving both monomer and polymer in a concentration from about 15 to about 35 percent (weight). The polymerization is carried out in a fiat mold, cg. between two glass or metal plates, using a promoted redox initiator (e.g. potassium pyrosulfite, ammonium persulfate and copper chloride) and cooling the mold in order to lead away the polymerization heat. The obtained clear, transparent sheet of highly elastic polymer, plastified with the salt solution, is then cut into thin strips which are then elastically stretched to 600-800 percent of their original length. Elastomeric monofilaments with circular cross section can be made similarly, using two grooved plates as a mold.

The coloring bath may contain, if desired, also usual wetting, dispersing, leveling, antistatic and other agents. Said agents may be also applied in a separate bath. if the dyeing or any subsequent bath is hot or boiling, the filaments may be additionally stretched therein. Such additional stretching and/or setting may be performed also at temperatures above 100 C. after drying, in a manner well known in the art.

The invention is illustrated, but not limited, by the following examples.

Example 1 200 ml. anhydrous pure acrylonitrile is dissolved in a mixture of 140 ml. aqueous zinc chloride solution (density 1.98 at 20 C.) and 76 ml. calcium chloride solution (density 1.42 at 20 C.). The solution is cooled down to 10 C. and the following components of a redox initiator are added while stirring: 2 ml. potassium pyrosulfate solution (2 percent) in an almost concentrated aqueous zinc chloride solution, 2 ml. ammonium persulfate solution of the same concentration in the same solvent, 5 drops of a 0.1 percent aqueous solution of copper dichloride dihydrate (CuCl lli O).

The thus initiated monomer solution is th n poured between two cooled, chromium-slated steel plates, provided on their borders with elastic spacing strips (soft rubber), thickness 2-3 mm. The mold is tightly closed and put into a cooling box. After three hours at l5 C. the polymerization is finished. The mold is left for an hour at room'temuerature and then taken apart. The sheet of transaprent, clear, tough rubbery mass is cut to strips of square cross section. The elastomeric filaments thus obtained are stretched to 800 percent of their original length, washed minutes at C. in circulating distilled water acidified with 0.1 percent hydrochloric acid in stretched condition, then further 5 minutes in a 2 percent solution of tartaric acid and immediately thereafter put into a 0.15 percent aqueous solution of Orange GG (Colour Index number 16,230, acid orange 10), maintained at 50 C. and stirred. After 10 minutes the filament, having a cross section of about 1 mm. is deeply orange colored. The monofilament is then shortly rinsed with water, dried at 6090 C. and set in dry condition at 120 C. for about 5 minutes without tension. The resulting orange colored monofilament is tough, strong, transparent and pliable. it shows an X-ray pattern of an oriented, crystalline polyacrylonitrile fibre.

. Example 2 10 kg. pulverized polyacrylonitrile, average molecular weight 95,000, aredissolved in 60 kg. aqueous zinc chloride solution (density 1.98 at 20 C.) at temperature gradually levated from 0 to 60 C. Into this solution concentrated aqueous calcium chloride solution (density 1.42 at 20 C.) are slowly added While The solution is then filtered at 4 5060 C. through a glass-fibre filter, deaerated at 20 mm. Hg and 50 C. and spun into a 15 percent aqueous solution of zinc and calcium chlorides, used in the same ratio as in the spinning dope. The spinneret with 0.8 mm. orifices is placed above the bath at a distance from about 1 to 70 millimeters. The rate of extrusion, of the take-oft", the path length in the bath and the temperature are regulated so as to obtain an intermediate rubbery filament containing 15 to 35 percent, more advantageously 20 to 25 percent of the polymer. After having been left standing for two hours in a comparatively dry room with a relative humidity of about 40 percent or less, the filament is elastically extended to about 400 percent of its original length and led continuously through a washing bath containing 0.1 percent hydrochloric acid and 0.1 percent Egacid Red G (Colour index number 18,050, acid red 1), the bath temperature being 20 C. The Washing and dyeing lasts 40 seconds, followed by three further baths consisting of distilled Water (or deior'zed water). One of them contains 2 percent citric acid. The two last baths have a temperature or" about C. The twisted and spooled deeply red colored filament is dried at 80 C. and then set at C. for 20 minutes.

Example 3 A 12 percent solution of polyacrylonitrile, average molecular weight 69,000, obtained by continual promoted redox polymerization in saturated zinc and calcium chlorides solution, is spun into a cold 2 percent solution of the same salts in a manner described in Example 2. The spun filament is deprived of adhering bath, continually air-dried and placed into a slowly rotating container by means of an ejector using compressed air. The filament contains then 25.5 percent polymer, 43 percent zinc chloride, 9.5 percent calcium chloride and 22 percent water. The filaments are almost purely elastomeric at room temperature. Since the salt plasticizcd filament is conductive, no troubles with static electricity will arise. The elastorneric filament is then elongated to 550 percent of its original length and led continuously through deionized water acidified with 0.1 percent hydrochloric acid. Then the filament is led continuously through a coloring bath containing 0.05 percent Orange GG (Colour Index number 16,230, acid orange 10) and 0.1 percent Amido Naphtol Red G (Colour Index number 18,050, acid red 1), urther through a rinsing bath, a bath containing 1 percent tartaric acid and finally through a 99 C. aqueous bath in which the filament is additionally stretched to percent. The filament is then cut into staple, dried and set at 120 C.

Similar good results are obtained with other acid dyestufis, e.g. with Alizarine Saphirol B (Colour Index Number 63,010, acid blue 45), Alizarine Cyanine green G-extra (Colour Index Number 61,570, acid green 25), Tartrazine (Colour Index number 19,140, acid yellow 23), direct pure blue 63 (Colour Index number 24,410, direct blue 1) etc. Very satisfying results are obtained also with basic, direct and acetate (dispersed) dyestuffs. Some dyestuffs may be also reused in alcoholic or other solutions. Developed azo-dyestufifs and vat-dyestuffs, e.g. those of the anthraquinone series, may be used in a continual two-baths process, yielding extremely 'fast colors.

Common acid dyestuffs prove a very high wash and light fastness, although the dyestuti is not bound chemically; probably the molecules of the dyestufi are very tightly held between the crystallineand semi-crystalline regions of the polymer.

Copolymers of acrylonitrile with a minor amount of e.g. vinyl acetate, methyl methacrylate, styrene, vinyl pyridine etc. can be used in the same Way, only the rate of taking the dyestufi from the bath is still higher. The period of time, during which such fibres may be .dyed after removing the greater part of the salts, is usually longer than with pure. polyacrylonitrile, as a result of a decreased crystallization rate. The dyeing process may be shortened to several seconds at room temperature so that it is very easy to join the spinning, wash, stretching and dyeing into a continuous process of high productivity. The possibility of using very cheap and fast acid dyestuffs is very important from the economical point of view. The costs of dyeing involve practically only the price of the dyestuft' without any further appreciable expenses.

It is to be mentioned, that dyeing of oriented articles from pure polyacrylonitrile may be carried out without difficulties by the present method, the copolymerization being not necessary for obtaining deep colors. This is of importance where the physical properties of the pure polyacrylonitrile fibre are to be maintained. No other method allows dyeing of pure acrylonitrile in oriented condition within one minute at room temperature, particularly with acid wool dyestuffs having one or more sulfonic groups in the molecule, without any additional processing steps or complex forming agents.

We claim:

1. A method of dyeing acrylic material of the type consisting of acrylonitrile polymers and copolymers containing at least 80 percent of an acrylonitrile component, comprising the steps of stretching an elastomeric elongated polymeric body consisting essentially of between and 35% of said acrylic material and of between 85 and 65 of a concentrated inorganic aqueous salt solution capable of dissolving said acrylic material, said elastomeric elongated polymeric body being due to the presence of said salt solution in a swollen gelled state; washing said elastomeric body at a temperature of up to about 50 C. while maintaining the same in stretched condition so as to remove at least a substantial part of said inorganic salt therefrom thereby at least substantially reducing the elastomeric properties of said stretched elongated polymeric body and initiating stabilization of the polymer structure thereof; and subjecting said elongated polymeric body to the action of a dye while said elongated polymeric body is still in swollen gelled state and stabilization of its polymer structure has not been completed.

2. A method of dyeing acrylic material of the type consisting of acrylonitrile polymers and copolymers containing at least 80 percent of an acrylonitrile component, comprising the steps of stretching to between 200 and 900% of its original len th an elastomeric elon ated ol meric body consisting essentially of between 15 and 35% of said acrylic material and of between 85 and 65% of a concentrated inorganic aqueous salt solution capable of dissolving said acrylic material, said elastomeric elongated polymeric body being due to the presence of said salt solution in a swollen gelled state; washing said elastomeric body at a temperature of up to about 50 C. while maintaining the same in stretched condition so as to remove at least a substantial part of said inorganic salt therefrom thereby at least substantially reducing the elastomeric properties of said stretched elongated polymeric body and initiating stabilization of the polymer structure thereof; and subjecting said elongated polymeric body to the action of a dye while said elongated polymeric body is still in swollen gelled state and stabilization of its polymer structure has not been completed.

3. -A method of dyeing acrylic material of the type consisting of acrylonitrile polymers and copolymers containing at least 80 percent of an acrylonitrile component, comprising the steps of stretching an elastomeric elongated polymeric body consisting essentially of between 15 and 35% of said acrylic material and of between 85 and 65 of a concentrated inorganic aqueous salt solution capable of dissolving said acrylic material, said elastomeric elongated polymeric body being due to the pres ence of said salt solution in a swollen gelled state; washing said elastomeric body at a temperature of up to about 50 C. while maintaining the same in stretched condition so as to remove at least a substantial part of said inorganic salt therefrom thereby at least substantially reducing the elastomeric properties of said stretched elongated polymeric body and initiating stabilization of the polymer structure of said elongated polymenic body; and subjecting said elongated polymeric body to the action of a dye within about 30 minutes after said washing of the same and while said elongated polymeric body is still in swollen gelled state and stabilization of its polymer structure has not been completed.

4. A method of dyeing acrylic material of the type consisting of acrylonitrile polymers and copolymers containing at least percent of an acrylonitrile component, comprising the steps of stretching an elastomeric elongated polymeric body consisting essentially of between 15 and 35% of said acrylic material and of between and 65% of a concentrated inorganic aqueous salt solution capable of dissolving said acrylic material, said elastomeric elongated polymeric body being due to the presence of said salt solution in a swollen gelled state; washing said elastomeric body at a temperature of up to about 50 C. while maintaining the same in stretched condition so as to remove at least a substantial part of said inorganic salt therefrom thereby at least substantially reducing the elastomeric properties of said stretched elongated polymeric body and initiating stabilization of the polymer structure of said elongated polymeric body; and subjecting said elongated polymeric body to the action of an acidic dyestuff having at least one sulfonic group in its molecule while said elongated polymenic body is still in swollen gelled state and stabilization of its polymer structure has not been completed.

5. A method of dyeing acrylic material of the type consisting of acrylonitrile polymers and copolymers containing at least 80 percent of an acrylonitnile component, comprising the steps of stretching an elastomeric elongated polymeric body consisting essentially of between 15 and 35% of said acrylic material and of between 85 and 65% of a concentrated inorganic aqueous salt solution capable of dissolving said acrylic material, said elastomeric elongated polymeric body being due to the presence of said salt solution in a swollen gelled state; washing said elastomeric body at a temperature of up to about 50 C. while maintaining the same in stretched condition so as to remove at least a substantial part of said inorganic salt therefrom thereby at least substantially reducing the elastomeric properties of said stretched elongated polymeric body and initiating stabilization of the polymer structure of said elongate-d polymeric body; and simultaneously subjecting said elongated polymeric body to the action of a dye While said elongated polymeric body is still in swollen gelled state and stabilization of its polymer structure has not been completed.

6. A method of dyeing acrylic material of the type consisting of acryloni-trile polymers and copolymers containing at least 80 percent of an acrylonitrile component, comprising the steps of stretching an elastomeric elongated polymeric body consisting essentially of between 15 35% of said acrylic material and of between 85 and 65% of a concentrated inorganic aqueous salt solution capable of dissolving said acrylic matenial, said elastomeric elongated polymeric body being due to the presence of said salt solution in a swollen gelled state; washing said elastomeric body at a temperature of up to about 50 C. while maintaining the same in stretched condition so as to substantially remove said inorganic salt therefrom thereby at least substantially reducing the elastomeric properties of said stretched elongated polymeric body and initiating stabilization of the polymer structure thereof; and simultaneously with said washing of said elongated polymeric body subjecting the same to the action of an acidic dyestufi having at least one sulfonic group in its molecule while said elongated polymeric body is still in swoll n gelled state and stabilization of its polymer structure has not been completed.

s,121,soe

7. A method of dyeing acrylic material of the type consisting of acrylonitrile polymers and copolymers containing at least 80- percent of acrylonitrile component, comprising the steps of stretching an elastomeric elongated polymeric body consisting essentially of between and of said acrylic material and of between 85 and of a concentrated inorganic aqueous salt solution capable of dissolving said acrylic material, said elastomeric elongated polymeric body being due to the presence of said salt solution in a swollen gelled state; washing said elastomeric body at substantially ambient temperature while maintaining the same in stretched condition so as to remove at least a substantial part of said inorganic salt therefrom thereby at least substantially reducing the elastomeric properties of said stretched elongated polymeric body and initiating stabilization of the polymer structure thereof; and subjecting said elongated polymeric body at substantially ambient temperatures to the action of a dye while said elongated polymeric body is still in swollen gelled state and stabilization of its polymer structure has not been completed.

8. A method of dyeing acrylic material of the type consisting of acrylonitrile polymers and copolymers containing at least percent of an acrylonitrile component, comprising the steps of stretching at substantially ambient temperature an elastomeric elongated polymeric body consisting essentially of between 15 and 35% of said acrylic material and or" between and 65% of a concentrated inorganic aqueous salt solution capable of dissolving said acrylic material, said elastomeric elongated polymeric body being due to the presence of said salt solution in a swollen gelled state; washing said elastomeiic body at a temperature of up to about 50 C. while maintaining the same in stretched condition so as to remove at least a substantial part of said inorganic salt therefrom thereby at least substantially reducing the elastomeric properties of said stretched elongated polymeric body and initiating stabilization of the polymer structure thereof; and subjecting said elongated polymeric body to the 5% action of a dye while said elongated polymeric body is still in swollen gelled state and stabilization of its polymer structure has not been completed.

9. A method of dyeing acrylic material of the type consisting of acrylonitrile polymers and copolymers containing at least 80 percent of an acrylonitrile component, comprising the steps of stretching at substantially ambient temperature to between about 200 and 900% of its original length an elastorneric elongated polymeric body consisting essentially of between 15 and 35% of said acrylic material and of between 85 and 65% of a concentrated inorganic aqueous salt solution capable of dissolving said acrylic material, said clastomeric elongated polymeric body being due to the presence of said salt solution in a swollen gelled state; washing said elastomeric body at substantially ambient temperature while maintaining the same in stretched condition so as to remove at least a substantial part of said inorganic salt therefrom thereby at least substantially reducing the elastomeric properties of said stretched elongated polymeric body and initiating stabilization of the polymer structure thereof; and simultaneously with said Washing of said elastomeric body subjecting the same at substantially ambient temperature to the action of an acidic dyestuil having at least one sulionic group in its molecule While said elongated poly- References Cited in the file of this patent UNITED STATES PATENTS V Cresswell July 3, 1951 2,558,733 2,558,735 Cresswell July 3, 1951 2,723,990 Hooper Nov. 15, 1955 

1. A METHOD OF DYEING ACRYLIC MATERIAL OF THE TYPE CONSISTING OF ACRYLONITRILE POLYMERS AND COPOLYMERS CONTAINING AT LEAST 80 PERCENT OF AN ACRYLONITRILE COMPONENT, COMPRISING THE STEPS OF STRETCHING AN ELASTOMERIC ELONGATED POLYMERIC BODY CONSISTING ESSENTIALLY OF BETWEEN 15 AND 35% OF SAID ACRYLIC MATERIAL AND OF BETWEEN 85 AND 65% OF A CONCENTRATED INORGANIC AQUEOUS SALT SOLUTION CAPABLE OF DISSOSLVING SAID ACRYLIC MATERIAL, SAID ELASTOMERIC ELONGATED POLYMERIC BODY BEING DUE TO THE PRESENCE OF SAID SALT SOLUTION IN A SWOLLEN GELLED STATE; WASHING SAID ELASTOMERIC BODY AT A TEMPERATURE OF UP TO ABOUT 50*C. WHILE MAINTAINING THE SAME IN STRETCHED CONDITION SO AS TO REMOVE AT LEAST A SUBSTANTIAL PART OF SAID INORGANIC SALT THEREFROM THEREBY AT LEAST SUBSTANTIALLY REDUCING THE ELASTOMERIC PROPERTIES OF SAID STRETCHED ELONGATED POLYMERIC BODY AND INITIATING STABILIZATION OF THE POLYMER STRUCTURE THEREOF; AND SUBJECTING SAID ELONGATED POLYMERIC BODY TO THE ACTION OF A DYE WHILE SAID ELONGATED POLYMERIC BODY IS STILL IN SWOLLEN GELLED STATE AND STABILIZATION OF ITS POLYMER STRUCTURE HAS NOT BEEN COMPLETED. 